Switches and other devices utilizing MEMS technology have recently become popular in the fiber optic communication industry due to their versatility, reproducibility, and durability. Conventional MEMS switches include a tiny reciprocating or pivoting mirror that requires a separate electrical power source to generate the voltage, e.g. 30V to 60V, required to move the mirror from a rest position to an active position. One such switch is disclosed in U.S. Pat. No. 6,303,885 issued Oct. 16, 2001 to Bryant Hichwa et al, which is incorporated herein by reference. The switch disclosed in the aforementioned reference is a bi-stable or latching MEMS switch that includes a mirror mounted on a reciprocating beam, which is supported by spring arms. Latching MEMS actuators generally only require a short duration, high voltage pulse to generate an electrostatic actuating force. However, due to the elastic nature of the arms supporting the beam with the mirror, the device tends to oscillate or “ring” before coming to a complete stop. To eliminate this ringing, breaking systems have been developed such as the one disclosed in U.S. patent application Ser. No. 09/810,825 filed Mar. 16, 2001 naming Mao et al as inventors, which is incorporated herein by reference. Unfortunately, these devices still require a steady high voltage source. Other devices using MEMS in the fiber optic communications industry include attenuators and dynamic gain equalizers.
The concept of using optical energy to actuate a switch is disclosed in U.S. Pat. No. 6,310,339 issued Oct. 30, 2001 in the name of Hsu et al; U.S. Pat. No. 5,714,773 issued Feb. 3, 1998 to Burrows et al; U.S. Pat. No. 5,859,719 issued Jan. 12, 1999 to Dentai et al; and U.S. Pat. No. 6,075,239 issued Jun. 13, 2000 to Aksyuk et al. Unfortunately, the Hsu et al device still requires a separate power source to provide a base voltage, to which the optical power is added to raise the total voltage over a threshold voltage, which actuates the switch. The remaining three references disclose devices that only generate very low voltages, and in reality would not be able to generate the energy required to power a conventional MEMS device, only simple specially designed devices.
An object of the present invention is to overcome the shortcomings of the prior art by providing a drive circuit for a conventional MEMS device that utilizes a low voltage source to generate a high voltage pulse.
Another object of the present invention is to provide an actuator for a MEMS switch that both drives and brakes the system with very little if any ringing.
Another object of the present invention is to provide a MEMS device that is powered by optical power only.
Another object of the present invention is to provide an efficient drive circuit that draws almost no current except during the short period of an optical switching cycle.
Another object of the present invention is to provide a drive circuit that does not need continuous optical power, only needing optical power when a switching cycle is anticipated.